土地覆被对气候影响的数值模拟实验  

Numerical Experiments on the Impact of Land Cover on Climate

作　　者：叶卓佳[1] 李克让[2] 黄玫[2] 

机构地区：[1]中国科学院大气物理研究所,北京100029 [2]中国科学院地理科学与资源研究所,北京100101

出　　处：《地理学报》2000年第B11期71-81,共11页Acta Geographica Sinica

基　　金：中国科技部"九五"重中之重项目!(969080305)&&

摘　　要：使用中尺度生态气象模式，并与积云对流参数化方案相结合，研究在不同的地形（平坦地形和复杂地形），不同天气背景（地转风为 ０．５ｍ／ｓ和 ５ｍ／ｓ，大气比湿分别为 ０．９， ０．８，０．７）条件下，中纬度半干旱地区陆面变化对中尺度大气边界层结构和气候的影响。研究表明：当在部分的裸壤地区为植物覆盖时，其下土壤将变得比其附近的干燥的裸壤湿润。在植物上空大气边界层内的温度比其附近的裸壤地区偏低，而大气湿度增加。由此，一个中尺度的水平气压扰动将产生，以适应热力场的扰动。在没有地转风的影响下，在该气压扰动的作用下，在大气边界层内，将产生从植物地区流向裸壤地区的植物风环流。陆面状况的变化引起风场、温度场和湿度场的扰动以及积云对流降水，将随地转风、大气背景湿度和陆面变化的程度而改变。在地形复杂地区，在不同的位置产生和发展植物风环流与山谷风环流的相互作用，可导致不同形式的气候变化。The impact of vegetation coverage on the mesoscale boundary layer structure of the midlatitude semiarid area has been investigated by using a mesoscale biological meteorological model coupled with a cumulus ensemble parameterization scheme over both a flat terrain and a complicated terrain under conditions with－ and without－synoptic flow and different background atmospheric humidity. The investigation indicates that regional perturbations in temperature and specific humidity over vegetation covered area from an adjacent dry, hair soil, caused by the water transpiration from vegetation and more evaporation from the underlying soil surface as compared to the adjacent dry, bare soil, since the soil covered by vegetation will be humider as compared to the bare soil. As a result, a positive pressure perturbation was created over vegetation area. A mesoscale circulation (called as vegetation breeze circulation, VBC) is forced over a flat terrain under calm synoptic condition by the horizontal pressure gradient with a wind speed reaching about 3. 2 m/s, directing from the vegetation area to the bare soil in the lower boundary layer. The regional climate over a flat terrain is greatly impacted by the VBC. Simulations also indicated that the convective precipitations were initiated and organized by vegetation －breeze circulations. The timing, location and strength of the precipitations will probably be controlled by the convergence zone associated with VBC's fronts and their interaction. Synoptic flow, atmospheric specific humidity and landscape changes played a significant role in modifying the structure and distribution of perturbations in wind, specific humidity, temperature and deep convective features (including convective clouds and precipitation). That is the reason why the deep convective precipitation event was considerably different day by day. The climate over a complex terrain is determined by the interactions between upslope flow circulation (UFC) and the VBC. Over a terrain defined as plain－slope�

关 键 词：土地覆被 数值模拟 中尺度环流 气候变化 

分 类 号：P461[天文地球—大气科学及气象学] P456.7